The present disclosure describes subject matter that relates to conductive films with particular discussion about conductive films comprising poly(3,4-ethylenedioxythiophene) (“PEDOT”).
Thin films and similar coatings and overlayments find use in many applications. For example, conductive films are found in a variety of consumer electronics (e.g., phones, televisions, tablet computers, videogames, etc.). These conductive films also enhance construction of solar cells, light-emitting diode (LED) devices, and other devices for use in many industrial applications.
Conductive films can utilize materials across a wide swath of conventional technologies. These materials can include, for example, silver nanowires, graphene, carbon nanotubes, micro-fine wire, metal mesh (embossed, directly printed, and etched), and similar nano-scale and micro-scale technologies. Many conductive films find particular use of indium tin oxide (ITO). In addition to favorable conductivity, this material affords the resulting conductive films with other characteristics (e.g., transparency) that make the films amenable to the wide range of applications mentioned above. ITO is, however, a product of indium, which is a raw material in relatively short supply and, accordingly, continues to increase in price with demand growth for thin, conductive films. Moreover, although favored for certain characteristics, films that utilize ITO can suffer from cracking and brittle failures when subject to bending. This feature somewhat limits use of these ITO-based films in combination, e.g., with flexible substrates.
Conductive polymers may address concerns with ITO-based films to provide candidate materials for use in connection with flexible electronics. For example, poly(3,4-ethylenedioxythophene) (also “PEDOT”) and like conjugated polymers are conducting polymers with good stability and optical transparency. These properties afford this polymer with suitable conductivity and transparency for use, e.g., in material layers on organic photovoltaics and LED devices. For other applications and/or manufacturing purposes, PEDOT often requires additional processes that synthesize the material to improve certain characteristics (e.g., conductivity) and/or properties (e.g., solubility). These processes may, for example, synthesize PEDOT in the presence of polystyrenesulfonate (PSS) to form solutions (also, “PEDOT:PSS solutions”) and/or initiate polymerization (e.g., vapor phase polymerization (also, “VPP”)), which results in films (also, “VPP:PEDOT films”) with attractive conductivity and transmission characteristics.